Elon Musk's first Boring Co. tunnel under Los Angeles is "almost done" and set to offer free rides to the public "in a few months," the CEO said late Thursday in an Instagram post.

"Super huge thanks to everyone that helped with this project," Musk said in a caption for a video racing through the tunnel. "Once fully operational (demo system rides will be free), the system will always give priority to pods for pedestrians and cyclists for less than the cost of a bus ticket."

The 2.7-mile L.A. tunnel would be first to be completed of four such projects. It's billed as a "proof-of-process" tunnel in the company's large-scale plans for reducing transportation congestion and travel times.

The company is also working on projects along the East Coast and in Chicago.

The tunnels will eventually be a paid alternative to buses or subways. The Instagram video, posted around 11 p.m. ET Thursday, had garnered 1.8 million views within 10 hours.

WATCH: Elon Musk's big ambitions may be killing Tesla

VIDEO5:3105:31

Tesla's earnings were better than expected, but Elon Musk still has a lot on his plate